This invention relates to centrefire sporting ammunition, especially but not exclusively shotgun cartridges, and in particular relates to the priming device which, as is well known, forms a constituent part of such ammunition and which, upon impact by the striker pin of a gun, initiates rapid burning of propellant which also forms part of the ammunition.
Typically, a conventional priming device comprises a cup-shaped member (often, as hereinafter, referred to as a "cap shell") containing a quantity of highly impact-sensitive priming material, the cap shell being provided with an anvil between the tip of which and the base of the cap shell there is a nip containing some of the priming material. Usually, the cap shell and the anvil are separately formed and the assembly thereof is referred to as a "battery pocket". In one known design of battery pocket the anvil is integrally formed with a second cup-shaped member (commonly referred to as a "cap chamber") which, when assembled with the priming material-containing cap shell co-axially engages the cap shell with the anvil extending into the latter towards the base thereof. The base of the cap chamber is provided with one or more apertures, commonly referred to as "flash holes" which, upon firing, allow flame from the priming material to reach, and initiate burning of, the propellant charge. In commercial operations, battery pockets are of course produced on a large scale, typically millions per week in the larger factories, and they are stored and transported in bulk for eventual incorporation in rounds of ammunition.
One problem that arises with the bulk storage and handling of battery pockets is that of mass-explosibility, that is to say the tendency of at least a significant proportion of a batch of proximate battery pockets to explode in response to accidental ignition of one of the pockets in the batch. It will be appreciated that such a tendency creates a potential danger, particularly to personnel. Hitherto, the problem has been dealt with by applying to the upper surface of the priming material, after drying thereof, a protective membrane of, for example, a paper foil and varnish, followed by incorporation of the anvil, the anvil often penetrating the membrane and extending into the priming material. Whilst this solves the problem of mass explosibility, it involves processing, in bulk, caps containing dangerous, dry priming material. In addition, the application of a foil and varnish is a somewhat exacting process.
It has already been proposed that the anvil may be incorporated with the cap shell before the priming material is dried, the water and/or other liquid medium present in the priming material being able to issue through the flash holes during a subsequent drying operation. Because wet priming materials are usually relatively safe to manipulate, that proposal mitigates the danger associated with incorporating the anvil into a cap shell containing dry priming material but, because of further processing difficulties, the application of known types of membrane for dealing with the mass explosibility problem is impracticable.
It is an object of the present invention to provide a battery pocket having acceptable mass-explosibility properties, which is simpler to produce compared to conventional methods and which may, if desired, be made by a method that takes advantage of the above-mentioned proposal, ie drying of the priming material after assembly of the battery pocket.